This invention relates to the detection of chemical vapors distributed in a region of the atmosphere. More specifically, the present invention is a system for the detection of chemical vapors in the atmosphere that directly exploits, in a novel manner, the basic physical principles of quantum mechanical absorption and emission by molecular structures at fixed frequencies determined by the physics of the particular molecular structure. Molecules exhibit the absorption of energy at discrete electromagnetic frequencies due to the quantum effect. Likewise, molecules exhibit emission of energy at discrete frequencies due to the quantum effect. In both absorption and emission, the energy absorbed or emitted is related to the frequency of the absorbed energy or the emitted energy by the fundamental physical constant known as Planks constant, denoted h; EQU Energy=h.times.(frequency)
Because of the quantum effect, a particular molecule in isolation will absorb energy at a limited number of fixed discrete frequencies only. These frequencies are known as absorption bands or absorption frequencies. A large number of chemicals have molecular structures having a multiplicity of absorption bands in the microwave frequency region from approximately one Gigahertz (10.sup.9 Hertz) to 100 Gigahertz (10.sup.11 Hertz). It is to these chemicals which may exist as a vapor distributed in the atmosphere that this present invention is addressed. National Bureau of Standards Monograph No. 70, entitled "Microwave Spectral Tables", Volume I through Volume 5, 1968, lists several hundred chemicals having absorption bands in the above mentioned region along with a tabulation of the absorption bands for each of the listed chemicals.
As background to the present invention, the following references are hereby cited:
In 1939, U.S. Pat. No. 2,165,214 was issued to Blau, et al. Blau et al teaches a method for the direct use of absorption band measurements in geophysical prospecting. Blau et al teaches the use of various portions of the electromagnetic spectrum, including light as well as the aforementioned microwave region, to directly measure the absorption frequencies.
In 1972, U.S. Pat. No. 3,651,395 was issued to Owen et al. Owen et al teaches the use of a system which exploits the frequency of radiation from excited hydrocarbon molecules to locate oil and gas deposits. Owen et al teaches the use of the frequency shift that results from highly exciting molecules causing them to emit at a frequency shifted by an amount determined by physics of the molecules from that of the frequency of the exciting energy. This frequency shift physical phenomena is known in the art as Raman Spectroscopy, see "Raman Spectroscopy" by D. A. Long, McGraw Hill, 1977 and, in general, do not correspond to the absorption frequencies.
In 1974, U.S. Pat. No. 3,803,595 was issued to McMillin. McMillin teaches the use of a poly-static system to locate molecules derived from petroleum.
In 1978, U.S. Pat. No. 4,100,481 was issued to Gournay. Gournay teaches a system for detecting and locating hydrocarbon gasses by the means of transmission and reception devices coupled with wide bandwidth and multiple channel narrow band processing devices.
In 1979, U.S. Pat. No. 4,132,943 was issued to Gournay, et al. Gournay, et al teaches an improvement over Gournay to determine the magnitude of the concentration of the hydrocarbon gas.